1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device and an electronic appliance including the semiconductor device.
Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification and the like relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. One embodiment of the present invention relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a storage device, a driving method thereof, or a manufacturing method thereof.
In this specification and the like, a semiconductor device generally means a device that can function by utilizing semiconductor characteristics. A semiconductor element such as a transistor, a semiconductor circuit, an arithmetic device, and a storage device are each an embodiment of a semiconductor device. An imaging device, a display device, a liquid crystal display device, a light-emitting device, an electro-optical device, a power generation device (including a thin film solar cell, an organic thin film solar cell, and the like), and an electronic appliance may each include a semiconductor device.
2. Description of the Related Art
Attention has been focused on a technique for forming a transistor using a semiconductor thin film formed over a substrate having an insulating surface (also referred to as a field-effect transistor (FET) or a thin film transistor (TFT)). Such transistors are applied to a wide range of electronic appliances such as an integrated circuit (IC) and an image display device (display device). A semiconductor material typified by silicon is widely known as a material for a semiconductor thin film that can be used in a transistor. As another material, an oxide semiconductor has been attracting attention (e.g., Patent Document 1).
A semiconductor device including, as a base insulating layer of an oxide semiconductor layer where a channel is formed, an insulating layer that releases oxygen by heating to reduce oxygen vacancy in the oxide semiconductor layer is disclosed (e.g., Patent Document 2).
A method for manufacturing a semiconductor device in which an oxide semiconductor layer is highly purified in the following manner is disclosed: an oxide insulating layer is formed over the oxide semiconductor layer; oxygen is taken (added) through the oxide insulating layer; heat treatment is performed; and impurities such as hydrogen, moisture, a hydroxyl group, or a hydride are removed from the oxide semiconductor layer by taking oxygen into the oxide semiconductor layer and performing the heat treatment (e.g., Patent Document 3).